docs: def _compute_distance(self, dists, C):
          """
          Compute the second term of the equation described on p. 1144:
  
          `` c4 * np.log(sqrt(R ** 2. + h ** 2.)
          """
          return C["c4"] * np.log(np.sqrt(dists.rrup ** 2. + C["h"] ** 2.))